The demands on wireless communication capabilities in today's society are increasing rapidly. In particular, fast and easily accessible communication is desired through hand-held devices over large areas. It is particularly challenging to achieve such communication for mobile devices which are moving, e.g. when moving over large distances with poor network coverage or when affected by unknown sources of noise interrupting a signal for communication, such as clients moving on e.g. trains, airplanes, and other types of moving vehicles. In particular, if a client, such as a mobile phone, moves over large areas the client has to connect to several base stations in order to maintain a sufficient connection for communication.
Further, e.g. train carriages are made of metal, and even the windows are normally covered with a metal film. Accordingly, train carriages are shielded compartments, and direct communication between terminal antennas within the carriages and externally located antennas is difficult to obtain.
The mobile nature of a client with respect to the base stations may also introduce several potential sources of communication performance degradation. Such sources may derive from complex terrain, competition for available channels, or the source may be an unknown source of noise related to e.g. radio-frequency interference.
At the same time, there is today an increasing demand from passengers to be able to communicate through mobile phones and other handheld terminals when travelling on e.g. trains, and also to be able to get access to the Internet with laptops, PDAs etc. Further, with the new smartphones, and the way these are used, with e.g. continuously operating applications, many phones are active at all times, meaning that many handovers are required when the train moves. Even though this problem is common for all moving vehicles, it is especially pronounced for vehicles moving at high speed, such as trains and airplanes, and trains are in addition facing problems with poor line-of-sight between the base stations and the train. This puts a strain on the wireless network infrastructure, leading to poor performance.
To this end, it is known to provide a mobile access router for data communication, also connected both to an external antenna and an internal antenna, in each carriage, in order to provide Internet access on board the vehicle. Such mobile access router solutions are e.g. commercially available from the applicant of the present application, Icomera AB, of Gothenburg, Sweden, and are also disclosed in EP 1 175 757 and WO 15/169917 by the same applicant. This method has greatly improved the reliability of high-bandwidth wireless communication for trains and other large vehicles.
However, this solution may still be insufficient to obtain an optimal transmission performance, especially for large data volumes. Trains and other moving vehicles often pass through areas with bad radio coverage, and present solutions are often unable to handle the required traffic. Further, the data traffic using cellular network communication, such as over 3G or 4G, is relatively costly.
Further, it is known to communicate with trains and other vehicles through dedicated base stations arranged sequentially along the rail track, and with a certain distance apart. Such base stations are generally referred to as trackside base stations or trackside access points, and typically operates with e.g. WLAN. However, trackside base stations may also operate in accordance with other protocols or standards, such as unlicensed LTE, licensed LTE, GSM-R, etc. However, trackside networks are extremely costly to implement, since the base stations need to be very close to each other, thereby requiring a very large number of base stations arranged close to the railway or road, and relatively evenly distributed. Thus, on the one hand trackside base stations cannot be arranged too far away from each other, since the performance deteriorates rapidly when the distance increases, however, on the other hand, closely arranged trackside base stations interfere with each other, making efficient communication problematic. Thus, implementation of trackside networks requires huge investments, and takes very long time. Despite this, it may still be difficult to obtain good coverage over the entire railway or road, and the communication performance may still be poorly and inadequate. The high costs are primarily related to the close arrangement of the base stations/access points, costs for building rather high radio towers, power to operate the base stations/access points and provision of fiber/radio link connections to the trackside network, such as the internet or a company specific networks. Thus, known trackside communication systems are very costly both to install and to operate.
There is therefore a need for an improved method and system for communicating with moving vehicles, and in particular trains, allowing increased capacity, capacity utilization, quality and/or cost-efficiency. Even though the above discussion is focused on trains, similar situations and problems are encountered in many other types of moving vehicles, and in particular moving passenger vehicles, such as buses, ships and airplanes.